Formulas: calculated fields
Some values should never be typed by hand — an expense total, a line amount, a mileage payout. A Formula_ sheet adds calculated fields: the app works these values out itself, so nobody mistypes a total. (The plural Formulas_ and Logic_ also work; Formula_ is the preferred spelling.) Write one formula per row across these columns: Output Field, Formula, Description, Section, Form. The output field is read-only and updates live while the record is being filled in.
Refer to fields by name, the way you would in a spreadsheet. A total that adds three expense fields is written hotel + meals + transport. On a form with a LINE ITEMS section, a formula can also roll a column up into a header field — sum of amount, count of amount, average of amount. A line formula can read a header value too: miles_driven * mileage_rate from HEADER. These roll-ups always read the record's own line items, so a form without a LINE ITEMS section can't use them. A number across many records — say, the average rating over all reviews — belongs on a dashboard instead; a formula row that asks for one is skipped, and the build tells you with a warning.
=B2*C2 arrives as the number Excel last saved, never as logic, and it will not recalculate in the app. Put calculations on the Formula_ sheet (or in a calc rule); sample rows should hold plain example values.| Which tool | Reach for it when | When it updates |
|---|---|---|
A formula — Formula_ sheet | You want arithmetic or IF-style decisions: totals, flags, bands | Live on screen, as the record is typed |
A calc rule — Rules sheet | You want to convert money or units: dollars to euros, pounds to kilograms | Each time the record is saved — the converted value is stored with the record |
calc rule. A Formula_ field is worked out in the browser and shown as you type — great for totals and on-screen logic. A calc rule (on the Rules sheet) is a currency/unit conversion the server computes and stores. Reach for a formula for arithmetic and IF/Boolean logic; reach for calc to convert money or units.Formulas can also make decisions, not only add numbers. Use IF(condition, value_if_true, value_if_false) together with AND, OR and NOT to pick a value from the data — for example, IF(total > 100, "High", "Low") flags every large claim for you, automatically and consistently.
Calculated fields are also recomputed on the server every time a record is saved. What you see in the browser is a live preview — the stored value always comes from the same formula run on the server, so a hand-edited total can never be submitted, on your forms or on a published public page.
The Formula reference lists every operator and function, with worked examples you can copy.